Many anatomic structures in the mammalian body are hollow passages in which walls of tissue define a central lumen, which serves as a conduit for blood, other physiologic fluids, nutrient matter, or waste matter passing within the structure. In many physiologic settings, dysfunction may result from a structural lumen which is either too large or too small. In most such cases, dysfunction can be relieved by interventional changes in the luminal size.
Thus in surgery, there is often a need to reduce the internal circumference of an orifice or other open anatomic structure to narrow the size of the orifice or opening to achieve a desired physiologic effect. Often, such surgical procedures require interruption in the normal physiologic flow of blood, other physiologic fluids, or other structural contents through the orifice or structure. The exact amount of the narrowing required for the desired effect often cannot be fully appreciated until physiologic flow through the orifice or structure is resumed. It would be advantageous, therefore, to have an adjustable means of achieving this narrowing effect, such that the degree of narrowing could be changed after its implantation, but after the resumption of normal flow in situ.
One example of a dysfunction within an anatomic lumen is in the area of cardiac surgery, and specifically valvular repair. Approximately one million open heart surgical procedures are now performed annually in the United States, and twenty percent of these operations are related to cardiac valves.
The field of cardiac surgery was previously transformed by the introduction of the pump oxygenator, which allowed open heart surgery to be performed. Valvular heart surgery was made possible by the further introduction of the mechanical ball-valve prosthesis, and many modifications and different forms of prosthetic heart valves have since been developed. However, the ideal prosthetic valve has yet to be designed, which attests to the elegant form and function of the native heart valve. As a result of the difficulties in engineering a perfect prosthetic heart valve, there has been growing interest in repairing a patient's native valve. These efforts have documented equal long-term durability to the use of mechanical prostheses, with added benefits of better ventricular performance due to preservation of the subvalvular mechanisms and obviation of the need for chronic anticoagulation. Mitral valve repair has become one of the most rapidly growing areas in adult cardiac surgery today.
Mitral valve disease can be subdivided into intrinsic valve disturbances and pathology extrinsic to the mitral valve ultimately affecting valvular function. Although these subdivisions exist, many of the repair techniques and overall operative approaches are similar in the various pathologies that exist.
Historically, most valvular pathology was secondary to rheumatic heart disease, a result of a streptococcal infection, most commonly affecting the mitral valve, followed by the aortic valve, and least often the pulmonic valve. The results of the infectious process are mitral stenosis and aortic stenosis, followed by mitral insufficiency and aortic insufficiency. With the advent of better antibiotic therapies, the incidence of rheumatic heart disease is on the decline, and accounts for a smaller percentage of valvular heart conditions in the developed world of the present day. Commissurotomy of rheumatic mitral stenosis was an early example of commonly practiced mitral valve repair outside of the realm of congenital heart defects. However, the repairs of rheumatic insufficient valves have not met with good results due to the underlying valve pathology and the progression of disease.
Most mitral valve disease other than rheumatic results in valvular insufficiency that is generally amenable to repair. Chordae rupture is a common cause of mitral insufficiency, resulting in a focal area of regurgitation. Classically, one of the first successful and accepted surgical repairs was for ruptured chordae of the posterior mitral leaflet. The technical feasibility of this repair, its reproducible good results, and its long-term durability led the pioneer surgeons in the field of mitral valve repair to attempt repairs of other valve pathologies.
Mitral valve prolapse is a fairly common condition that leads over time to valvular insufficiency. In this disease, the plane of coaptation of the anterior and posterior leaflets is “atrialized” relative to a normal valve. This problem may readily be repaired by restoring the plane of coaptation into the ventricle.
The papillary muscles within the left ventricle support the mitral valve and aid in its function. Papillary muscle dysfunction, whether due to infarction or ischemia from coronary artery disease, often leads to mitral insufficiency (commonly referred to as ischemic mitral insufficiency). Within the scope of mitral valve disease, this is the most rapidly growing area for valve repair. Historically, only patients with severe mitral insufficiency were repaired or replaced, but there is increasing support in the surgical literature to support valve repair in patients with moderate insufficiency that is attributable to ischemic mitral insufficiency. Early aggressive valve repair in this patient population has been shown to increase survival and improve long-term ventricular function.
In addition, in patients with dilated cardiomyopathy the etiology of mitral insufficiency is the lack of coaptation of the valve leaflets from a dilated ventricle. The resultant regurgitation is due to the lack of coaptation of the leaflets. There is a growing trend to repair these valves, thereby repairing the insufficiency and restoring ventricular geometry, thus improving overall ventricular function.
The two essential features of mitral valve repair are to fix primary valvular pathology (if present) and to support the annulus or reduce the annular dimension using a prosthesis that is commonly in the form of a ring or band. The problem encountered in mitral valve repair is the surgeon's inability to fully assess the effectiveness of the repair until the heart has been fully closed, and the patient is weaned off cardiopulmonary bypass. Once this has been achieved, valvular function can be assessed in the operating room using transesophageal echocardiography (TEE). If significant residual valvular insufficiency is then documented, the surgeon must re-arrest the heart, re-open the heart, and then re-repair or replace the valve. This increases overall operative, anesthesia, and bypass times, and therefore increases the overall operative risks.
If the prosthesis used to reduce the annulus is larger than the ideal size, mitral insufficiency may persist. If the prosthesis is too small, mitral stenosis may result. The need exists, therefore, for an adjustable prosthesis that would allow a surgeon to adjust the annular dimension in situ in a beating heart under TEE guidance or other diagnostic modalities to achieve optimal valvular sufficiency and function.
Cardiac surgery is but one example of a setting in which adjustment of the annular dimension of an anatomic orifice in situ would be desirable. Another example is in the field of gastrointestinal surgery, where the Nissen fundoplication procedure has long been used to narrow the gastro-esophageal junction for relief of gastric reflux into the esophagus. In this setting, a surgeon is conventionally faced with the tension between creating sufficient narrowing to achieve reflux control, but avoiding excessive narrowing that may interfere with the passage of nutrient contents from the esophagus into the stomach. Again, it would be desirable to have a method and apparatus by which the extent to which the gastro-esophageal junction is narrowed could be adjusted in situ to achieve optimal balance between these two competing interests.
Aside from the problem of adjusting the internal circumference of body passages in situ, there is often a need in medicine and surgery to place a prosthetic implant at a desired recipient anatomic site. For example, existing methods proposed for percutaneous mitral repair include approaches through either the coronary sinus or percutaneous attempts to affix the anterior mitral leaflet to the posterior mitral leaflet. Significant clinical and logistical problems attend both of these existing technologies. In the case of the coronary sinus procedures, percutaneous access to the coronary sinus is technically difficult and time consuming to achieve, with procedures which may require several hours to properly access the coronary sinus. Moreover, these procedures employ incomplete annular rings, which compromise their physiologic effect. Such procedures are typically not effective for improving mitral regurgitation by more than one clinical grade. Finally, coronary sinus procedures carry the potentially disastrous risks of either fatal tears or catastrophic thrombosis of the coronary sinus.
Similarly, percutaneous procedures which employ sutures, clips, or other devices to affix the anterior mitral leaflets to the posterior mitral leaflets also have limited reparative capabilities. Such procedures are also typically ineffective in providing a complete repair of mitral regurgitation. Furthermore, surgical experience indicates that such methods are not durable, with likely separation of the affixed valve leaflets. These procedures also fail to address the pathophysiololgy of the dilated mitral annulus in ischemic heart disease. As a result of the residual anatomic pathology, no ventricular remodeling or improved ventricular function is likely with these procedures.
The need exists, therefore, for a delivery system and methods for its use that would avoid the need for open surgery in such exemplary circumstances, and allow delivery, placement, and adjustment of a prosthetic implant to reduce the diameter of such a mitral annulus in a percutaneous or other minimally invasive procedure, while still achieving clinical and physiologic results that are at least the equivalent of the yields of the best open surgical procedures for these same problems.
The preceding cardiac applications are only examples of some applications according to the present invention. Another exemplary application anticipated by the present invention is in the field of gastrointestinal surgery, where the aforementioned Nissen fundoplication procedure has long been used to narrow the gastro-esophageal junction for relief of gastric reflux into the esophagus. In this setting, a surgeon is conventionally faced with the tension between creating sufficient narrowing to achieve reflux control, but avoiding excessive narrowing that may interfere with the passage of nutrient contents from the esophagus into the stomach. Additionally, “gas bloat” may cause the inability to belch, a common complication of over-narrowing of the GE junction. An adjustable prosthetic implant according to the present invention could allow in situ adjustment in such a setting under physiologic assessment after primary surgical closure. Such an adjustable prosthetic implant according to the present invention could be placed endoscopically, percutaneously, or with an endoscope placed within a body cavity or organ, or by trans-abdominal or trans-thoracic approaches. In addition, such an adjustable prosthetic implant according to the present invention could be coupled with an adjustment means capable of being placed in the subcutaneous or other anatomic tissues within the body, such that remote adjustments could be made to the implant during physiologic function of the implant. This adjustment means can also be contained within the implant and adjusted remotely, i.e. remote control adjustment. Such an adjustment means might be capable of removal from the body, or might be retained within the body indefinitely for later adjustment.
The present invention and the methods for its use anticipate many alternate embodiments in other potential applications in the broad fields of medicine and surgery. Among the other potential applications anticipated according to the present invention are adjustable implants for use in the treatment of morbid obesity, urinary incontinence, anastomotic strictures, arterial stenosis, urinary incontinence, cervical incompetence, ductal strictures, and anal incontinence. The preceding discussions are intended to be exemplary embodiments according to the present invention and should not be construed to limit the present invention and the methods for its use in any way.